1. Field of the Invention
The present invention relates to a dismountable toroidal support for tyre manufacture, of the type comprising: a plurality of sectors circumferentially aligned around a geometric reference axis to define an outer surface substantially reproducing the inner conformation of a tyre being processed; a flange carrying at least one attachment member for engagement with a handling device; a counter-flange to be operatively linked with said flange at an axially opposite position; engagement devices for fixedly holding the sectors between said flange an, counter-flange.
2. Description of the Related Art
Production of a tyre for vehicle wheels essentially involves a manufacturing step in which the different constructional elements of the tyre are assembled following a preestablished sequence, and a subsequent vulcanization step in which, through pressing within a mould and simultaneous administration of heat, molecular cross-linking of the elastomer material employed in forming said constructional elements is caused, which will, as a result, bring about structural and dimensional stabilization of the tyre itself.
It should be pointed out, for the purposes of the present description, that by the term xe2x80x9celastomer materialxe2x80x9d it is intended the rubber blend in its entirety, i.e. the assembly formed of at least one base polymer suitably amalgamated with reinforcing fillers and process additives of various types.
The traditional production methods essentially involve that the constructional elements of the tyre, such as carcass plies, anchoring annular structures for the tyre beads, belt structure, sidewalls, tread band, etc. should be first made separately from each other, to be then sequentially assembled during the tyre manufacturing process.
The Applicant""s present trend is however that of resorting to manufacturing methodologies enabling production and storage of semifinished products to be minimized or, possibly, eliminated.
Practically, research and development are presently addressed to new process solutions enabling the individual components to be made by directly forming them on the tyre being manufactured according to a preestablished sequence.
In this connection, manufacturing processes have been recently proposed and developed, by the Applicant itself as well, in which assembling of the components during the tyre manufacture takes place on a rigid toroidal support which is then introduced into a vulcanization press together with the tyre to be cured. When vulcanization has been completed, the rigid toroidal support must be removed from the tyre previously extracted from the vulcanizing unit.
To enable this removal, use of collapsible or dismountable toroidal supports is usually provided, which supports are made up of a plurality of circumferential sectors lending themselves to be individually retracted in a radial direction towards the rotation axis of the tyre for disengagement from the tyre itself passing through the space defined between the tyre beads.
Such a dismountable toroidal support is described in U.S. Pat. No. 4,106,888 for example, where provision is made for the presence of a first and a second series of circumferential sectors disposed in alternated relationship with each other and connected to respective linkages that, during a first step, carry out a radial translation inwardly of the tyre of the sectors belonging to the first series and axially extract said sectors from the tyre itself, in order to free the required space for radial translation of the sectors belonging to the second series which is accomplished during a subsequent step.
To avoid too many stresses being imposed to the tyre during radial translation of the sectors, appropriate grip members cause the tyre beads to be mutually open wide in an axial direction to enable extraction of the sectors in the absence of interference.
In document U.S. Pat. No. 4,116,596, in order to limit stresses on the tyre, the individual sectors are provided to have a structure which can contract in a radial direction, so that said sectors can pass between the tyre beads without the latter being required to open too wide.
Document EP 893 237 discloses a dismountable toroidal support in which mutual connection between the circumferential sectors is ensured by two axially opposite annular flanges that are kept in axial thrust relationship on opposite sides of the toroidal support by a cylindrical sleeve axially extending through the toroidal support itself. One end of the cylindrical sleeve acts against one of the flanges by means of a circumferential abutment, whereas the opposite end gets operatively in engagement with the other flange by screwing or bayonet coupling.
Removal of the toroidal support from the cured tyre involves that, at a dismantling station in which engagement of the tyre has been previously carried out, the cylindrical sleeve together with one of the flanges should be disengaged from the counter-flange and associated with a counter-flange and respective circumferential sectors previously arranged in an adjacent assembling station in order to constitute a new toroidal support which will be subsequently moved away. The tyre, together with the circumferential sectors of the toroidal support, is temporarily removed from the dismantling station to enable transfer of the counter-flange to the assembling station. When transferring is over, the tyre is engaged again in the dismantling station to enable removal of the circumferential sectors. Each sector is extracted from the tyre by a centripetal radial movement, to be subsequently transferred onto a respective support element arranged in the assembling station. When all sectors have been transferred to the assembling station, a radial movement of the respective support elements causes the same to circumferentially move close to each other, so that they are ready to engage a new sleeve with the respective flange, which have been removed from she toroidal support associated with the subsequent tyre transferred to the dismantling station.
In accordance with the present invention, it has been found that if a substantially U-shaped conformation in section is given to the toroidal support, important advantages can be achieved both in terms of quality of the finished product, particularly in connection with the consequent optimization of the curing process, and in terms of simplification of the disassembling and/or reassembling operations of the toroidal support at the end of the curing process.
More particularly, it is an object of the present invention to provide a dismountable toroidal support for tyre manufacture, characterized in that each of said sectors has a main body with a substantially U-shaped outline seen in cross-section, which is delimited between an outer side defining said outer surface, and an inner side facing said geometric reference axis, said engagement devices comprising, for each of said sectors, at least one attachment plate radially projecting from the inner side substantially in a plane normal to said geometric reference axis, and adapted to be removably engaged at a position axially interposed between said flange and counter-flange.
In more detail, the attachment plate of each sector substantially extends in an equatorial plane of the toroidal support and is preferably provided with at least one auxiliary through slot extending close to the inner side of the main body.
It may be also provided that along the inner side of the main body of each sector at least one draining section should be formed which extends from an inner circumferential edge of the toroidal support and gradually converges towards an equatorial plane of said toroidal support away from said geometric reference axis.
In a preferential embodiment, the engagement devices further comprise: connecting pins distributed around said geometric reference axis and having each an end head to be axially fitted through a through housing arranged in one of said attachment plates; hooking members to be operatively engaged each with the end head of one of said connecting pins to axially lock the attachment plate of one of said sectors between said flange and counter-flange.
In more detail, the connecting pins are preferably integral with said flange and said hooking members are operatively carried by said counter-flange.
The hooking members can be advantageously formed in a closure ring carried by the counter-flange and susceptible of rotation around the geometric reference axis.
Preferably, said engagement devices further comprise counter-bushes and spring elements operating on the counter-bushes to axially push them against the attachment plates of the sectors.
More specifically, the counter-bushes and said spring elements are operatively carried by the counter-flange, said counter-bushes being adapted to be axially fitted on the end heads of said connecting pins.
In accordance with a preferential embodiment, each of said through housings formed in said attachment plates has flared ends arranged to engage tapered portions carried by said connecting pins and counter-bushes, respectively.
In addition, each of said attachment plates is provided to further have at least one auxiliary fitting housing extending in parallel with said through housing for engagement of locating pegs provided on an apparatus for disassembling and reassembling of the toroidal support itself.